1. Field of the Invention
The present invention generally relates to racks, particularly, to a rack used to hold workpieces during ultrasonic washing.
2. Discussion of the Related Art
Ultrasonic washing is widely used for cleaning workpieces. During washing, the workpieces are fixed on racks and the racks are placed into a washing liquid. The washing liquid is then vibrated ultrasonically by an ultrasonic generator and the workpieces are cleaned by the vibration of the washing liquid.
Referring to FIG. 5 and FIG. 6, a typical rack 500 includes a frame 51 and a plurality of retainers 52 fixed on the frame 51. Each retainer 52 includes two opposite flexuous first arms 521 and a flexuous second arm 522 installed below the first arms 521. Each first arm 521 and second arm 522 zigzags, thus forming a plurality of first V-shaped portions 5211 on each first arm 521 and a plurality of second V-shaped portions 5221 on the second arm 522. The apex of the V's, of each first V-shaped portions 5211 and each second V-shaped portions 5221, align with each other. One second V-shaped portion 5221 cooperates with two corresponding first V-shaped portions 5211 to define a fixing space (not labeled). Thus a workpiece 53 can be fixed in the fixing space. In this way, the typical rack 500 can accommodate a plurality of workpieces 53 therein.
However, some workpieces, such as a housing of a mobile phone, generally, includes a polished portion formed on a side of the housing. When the workpiece is being placed on the rack 500, the polished portion comes into contact with the first arms 521 and the second arm 522. Thus, the polished portion may be scratched, by the first arms 521 and/or the second arm 522, when being mounted, removed, or during washing of the workpiece.
Therefore, an improved rack is desired in order to overcome the above-described shortcomings.